How to maintain smooth curves on meshes with lots of uneven loopcuts?
IMHO, it is hardly possible to keep that curve exactly the same as what it is after adding support loop, unless you take GiantCowFilms' second way, though it will bring new problem for subdivision. However, you can make the difference unnoticeable:



You can either do this by sliding GG or ShiftV on each side; or, select both sides, then W > Smooth, tweak levels and axes in F6 panel.